Mist suppressant for solvent extraction metal electrowinning

Abstract

The formation of acid mist or spray over metal electrowinning tanks, such as in the electrowinning of copper obtained by solvent extraction, is substantially inhibited or eliminated by electrowinning the metal from electrolyte containing certain cationic and/or amphoteric fluoroaliphatic surfactants.

What is claimed is: 
     
       1. A process for recovery of metal values by liquid-liquid solvent extraction of said metal values from metal-bearing aqueous solution, stripping of said metal values into acidic aqueous solution containing strong acid, and electrowinning of said metal values from an electrolytic cell, said cell comprising a metallic cathode, one or more insoluble anodes, and electrolyte containing said strong acid and said metal values, said process including recycling of said electrolyte, wherein the improvement comprises electrowinning said metal values from electrolyte containing sufficient fluoroaliphatic surfactant to provide mist-inhibiting foam on the surface of said electrolyte, said surfactant having at least one cationogenic group which is the radical of a base having an ionization constant in water at 25° C. of at least about 10 -6 , and containing at least about 30 weight percent fluorine in the form of carbon-bonded fluorine in a fluoroaliphatic radical, said fluoroaliphatic radical having at least 4 carbon atoms and at least a terminal perfluoromethyl group. 
     
     
       2. A process according to claim 1, wherein said surfactant also has at least one anionogenic group which is the radical of an acid having an ionization constant in water at 25° C. of at least about 10 -6 . 
     
     
       3. A process according to claim 1, wherein said metal values comprise nickel. 
     
     
       4. A process according to claim 1, wherein said metal values comprise copper. 
     
     
       5. A process according to claim 1, wherein said surfactant comprises compounds of the formula: ##STR9## wherein: a is independently 0 or 1; b is 1 or 2;   R f  is a fluorinated, monovalent, aliphatic radical, with the proviso that the molecule contains about 30 weight percent fluorine in the form of carbon-bonded fluorine in R f  ;   Q is independently a linking group, with the proviso that at least one Q group is present in the molecule;   R 3  is independently: R 4  wherein R 4  is H or alkyl;   (Q) a  AM wherein A is --COO - , --SO 3   - , --OSO 3   - , --PO 3  H - , or --OPO 3  H - , and M is H + , a metal ion, or N +  (R 1 ) 4  where each R 1  is independently H or alkyl; or   QNR 5  R 6  R 7  wherein R 5  and R 6  are independently H, alkyl, or together with the N atom to which R 5  and R 6  are attached form a cyclic ring, and R 7  is R 4 , a quaternary ammonium group, or (Q) a  AM;     Z is --CO-- or --SO 2  --; and   X is halogen, hydroxide, sulfate, bisulfate, or carboxylate.   
     
     
       6. A process according to claim 5, wherein said surfactant comprises compounds of the formula: ##STR10## wherein R f  contains about 4 to 8 carbon atoms, Q is alkylene or hydroxyalkylene, A is --COO -   or --SO 3   - , and R 5 , R 6 , and R 7  are alkyl or hydroxyalkyl. 
     
     
       7. A process according to claim 5, wherein said surfactant comprises compounds of the formula: ##STR11## wherein R f  contains about 4 to 12 carbon atoms, Q is alkylene, R 5  and R 6  are lower alkyl, and R 7  is carboxyalkylene. 
     
     
       8. A process according to claim 2, wherein said surfactant comprises about 1 to 200 parts by weight [C 6  F 13  SO 2  N(CH 2  CHOHCH 2  SO 3  Na)C 3  H 6  N +  (CH 3 ) 2  C 2  H 4  OH]OH -  per one million parts by weight of said electrolyte. 
     
     
       9. A process according to claim 2, wherein said surfactant comprises about 1 to 200 parts by weight C 6  F 13  SO 2  N(CH 2  CHOHCH 2  SO 3  Na)C 3  H 6  N(CH 3 ) 2  per one million parts by weight of said electrolyte. 
     
     
       10. A process for the recovery of metal values from metal-bearing aqueous solutions, comprising the steps of: (a) mixing said metal-bearing aqueous solution with water-immiscible organic solvent containing water-insoluble organic ion exchange composition, said composition having selective affinity for said metal values, thereby forming metal-bearing organic solution and metal-depleted aqueous solution;   (b) separating said metal-bearing organic solution and said metal-depleted aqueous solution;   (c) contacting said metal-bearing organic solution with aqueous strip solution comprising strong acid and less than or equal to 0.02 weight percent of fluoroaliphatic surfactant, said surfactant having at least one cationogenic group which is the radical of a base having an ionization constant in water at 25° C. of at least about 10 -6 , and containing at least about 30 weight percent fluorine in the form of carbon-bonded fluorine in a fluoroaliphatic radical, said fluoroaliphatic radical having at least 4 carbon atoms and at least a terminal perfluoromethyl group, thereby forming metal-enriched aqueous strip solution and metal-depleted organic solution, said metal-enriched aqueous strip solution having a surface tension at 25° C. which is less than or equal to about 35 dynes/cm;   (d) separating said metal-depleted organic solution and said metal-enriched aqueous strip solution;   (e) electroplating said metal values onto a metallic cathode using said metal-enriched aqueous strip solution as electrolyte in an electrolytic bath, by passing direct electric current between said cathode and an insoluble anode or anodes, with the surface of said electrolytic bath being wholly or partly covered with foam formed from the interaction of said electrolyte, oxygen evolved from said electrolyte at said anode or anodes, and/or air or other gas entrained in said electrolyte, said foam suppressing misting of said electrolyte and release of said electrolyte into the atmosphere surrounding said electrolytic bath; and   (f) recycling the resulting metal-depleted electrolyte for use as aqueous strip solution in step (c).   
     
     
       11. A process according to claim 10, wherein said surfactant also has at least one anionogenic group which is the radical of an acid having an ionization constant in water at 25° C. of at least about 10 -6 . 
     
     
       12. A process according to claim 10, wherein said metal comprises nickel. 
     
     
       13. A process according to claim 10, wherein said metal comprises copper. 
     
     
       14. A process according to claim 10, wherein said surfactant comprises compounds of the formula: ##STR12## wherein: a is independently 0 or 1; b is 1 or 2;   
     
     
       R f  is a fluorinated, monovalent, aliphatic radical, with the proviso that the molecule contains about 30 weight percent fluorine in the form of carbon-bonded fluorine in R f  ; Q is independently a linking group, with the proviso that at least one Q group is present in the molecule;   R 3  is independently: R 4  wherein R 4  is H or alkyl;   (Q) a  AM wherein A is --COO - , --SO 3   - , --OSO 3   - , --PO 3H   - , or --OPO 3  H - , and M is H + , a metal ion, or N +  (R 1 ) 4  where each R 1  is independently H or alkyl; or   QNR 5  R 6  R 7  wherein R 5  and R 6  are independently H, alkyl, or together with the N atom to which R 5  and R 6  are attached form a cyclic ring, and R 7  is R 4 , a quaternary ammonium group, or (Q) a  AM;     Z is --CO-- or --SO 2  --; and   X is halogen, hydroxide, sulfate, bisulfate, or carboxylate.   
     
     
       15. A process according to claim 14, wherein said surfactant comprises compounds of the formula: ##STR13## wherein R f  contains about 4 to 8 carbon atoms, Q is alkylene or hydroxyalkylene, A is --COO -  or --SO 3   - , and R 5 , R 6 , and R 7  are alkyl or hydroxyalkyl. 
     
     
       16. A process according to claim 14, wherein said surfactant comprises compounds of the formula: ##STR14## wherein R f  contains about 4 to 12 carbon atoms, Q is alkylene, R 5  and R 6  are lower alkyl, and R 7  is carboxyalkylene. 
     
     
       17. A process according to claim 11, wherein said surfactant comprises about 1 to 200 parts by weight [C 6  F 13  SO 2  N(CH 2  CHOHCH 2  SO 3  Na)C 3  H 6  N +  (CH 3 ) 2  C 2  H 4  OH]OH -  per one million parts by weight of said strip solution. 
     
     
       18. A process according to claim 11, wherein said surfactant comprises about 1 to 200 parts by weight C 6  F 13  SO 2  N(CH 2  CHOHCH 2  SO 3  Na)C 3  H 6  N(CH 3 ) 2  per one million parts by weight of said strip solution.